Nature Genetics pp 1253 - 1257

Malaria has exerted large selective force on human populations, including the selection for genes that protect against malaria infection. A study in the November issue of Nature Genetics now shows that co-inheritance of two of the most common genetic variants, which individually confer protection, may cancel the protective effects.

Tom Williams and colleagues found that children with both variants show no increased protection from malaria infection, while children with only a single variant showed increased protection. The study compared the rates of developing severe malaria in two cohorts of children in Kenya, categorized by these two genetic traits. The genetic traits considered were sickle cell trait and α+ thalassemia, two prevalent genetic variants in sub-Saharan Africa, that individually confer protection from malaria. Hemoglobin, a protein required for the transport of oxygen by red blood cells, is altered in both conditions. Sickle trait alters the beta subunit of hemoglobin, while α+ thalassemia, the most common of thalassemias, affects the α chain of hemoglobin.